Electric switch for sensing swimming race events and the like

ABSTRACT

A fluid damped, submersible switch for sensing swimming race events comprising multiple stacked conductive plates separated by thin nonconductive spacers. At least some of the plates are resiliently bendable, when touched to contact another of the plates. Fluid passages through an outer one of the plates permits restricted fluid flow from between the switch plates and the environment surrounding the switch. An interface circuit between the poles of the switch and a voltage source normally maintains the voltage level applied between the switch poles at a sufficiently low value to prevent fluid ionization and current flow through the fluid between the switch plates when the plates are separated, and permits current flow when plates of opposite polarity are touching.

i United States Patent [1 1 Coble, Jr. et al.

[ 1 ELECTRIC SWITCH FOR SENSING SWIMMING RACE EVENTS AND THE LIKE [76] Inventors: Ralph Parker Coble, Jr., 271 l Tillbrook Place; Ralph Rabun Allred, 2705 Asbury Terrace, both of Greensboro, N.C. 27408 22 Filed: Dec. 7, 1973 21 Appl. No.: 422,977

[52] US. Cl 307/119; 200/52 R; 340/323 R;

272/4 [51] Int. Cl. HOlI-l 35/00 [58] Field of Search 307/1 19, 116, 113, 112,

307/253, 254, 247 A; 200/52 R, 85 R, 86 R; 272/59 R, 59 A, 4; 340/323 R [56] References Cited UNITED STATES PATENTS 3,001,120 9/1961 Bereskin 321/16 3,230,325 l/l966 Parkinson .1 200/52 R 3,371,228 2/1968 Murray 307/254 3,784,768 l/1974 Hunt 200/86 R Primary ExaminerRobert K. Schaefer Assistant Examiner-M. Ginsburg 5 7 ABSTRACT A fluid damped, submersible switch for sensing swimming race events comprising multiple stacked conductive plates separated by thin nonconductive spacers. At least some of the plates are resiliently bendable, when touched to contact another of the plates. Fluid passages through an outer one of the plates permits restricted fluid flow from between the switch plates and the environment surrounding the switch. An interface circuit between the poles of the switch and a voltage source normally maintains the voltage level applied between the switch poles at a sufficiently low value to prevent fluid ionization and current flow through the fluid between the switch plates when the plates are separated, and permits current flow when plates of opposite polarity are touching.

11 Claims, 15 Drawing Figures Sheet 1 of5 U.S. Patent Oct. 28, 1975 FIG].

Sheet 2 of 5 US. Patent Oct. 28, 1975 U.S. Patent Oct.28, 1975 Sheet? of5 3,916,214

US. Patent Oct. 28, 1975 Sheet4of 5 3,916,214

US. Patent Oct. 28, 1975 Sheet50f5 3,916,214

FIG/2.

VOLTAGE v/ SOURCE F/ 61 /3.

OUTPUT TO JUDGING AND TIMING CIRCUITS INPUT ELECTRIC SWITCH FOR SENSING SWIMMING RACE'EVENTS AND THE LIKE The present invention relates to an improved electrical switch used in automatic timing and sequence indicating systems, such as an automatic judging and timing system with a relay take-off judging feature for determining: the number of laps each contestant makes; the elapsed times of individual contestants; rank order of finish; whether a contestant touches the end of the lane during a swimming event lap; and whether a swimmer leaves the starting block prior to his teammate s touch on the end of the lane during a swimming relay event; and reaction tests in research laboratories. The system is primarily adaptable for swimming and track races; however, it fulfills the need of many types of automatic timing and sequence requirements.

Historically, the problem of determining accurately the finish and elapsed times of contestants in swimming and track races has been very difficult. Also, in swimming relay events, the outstanding problem has been to determine if an incoming swimmer has touched the end of the lane prior to this teamates foot leaving the starting block. In addition, for swimming races, judges have had difficulty determining if a swimmer touches the end of the lane during his turns and if he makes the correct number of laps. For swimming uses, these problems are aggravated by the fact that a swimmer may touch either below or above the water surface and, during a turn, will create waves and splashes which obscure the judges vision. The difiiculty of humans trying to rank order the finish is also overcome with this invention. Since the touch of each swimmer is recognized by the lane switch in that particular lane, the order of finish is computed to an accuracy of 1X10 seconds by the electronic circuits and appropriately displayed.

Previous attempts to solve the above problems have used lane switches which were filled with nonconducting fluid and sealed. This type of system did not allow the swimmers to make a turn while the switch was in position; therefore, the switches were held out of position until the swimmer had completed the appropriate number of laps and then moved into position during the final lap in order to accept the final touch. This resulted in many human errors and malfunctions. US. Pat. No. 3,230,325, issued Jan. 18, 1966 to W. C. Parkinson, is illustrative of the older type of switch. Other types of systems have used moving plates and mechanical switches which have also been unreliable.

The starting block and lane switches covered by this invention solve the previous problems by incorporating the following features into the design:

1. The open circuit resistance of the switch is low compared to the resistance of the medium, usually pool water, with which it is used.

2. The switch is highly sensitive to concentrated pressure, such as a finger, hand, or foot touch, and not sensitive to widely distributed loads, such as waves and splashes.

3. The medium in which the switch is submerged, partially submerged, or in the same vicinity with, along with the surrounding air is utilized for damping of the switch action. The switch istherefore, not sealed from the surrounding environment.

4. The switches are sensitive to a light touch on the front, top, and formed edges. Other type switches were not sensitive except in the flat area on the front. 1

5. The lane switches and starting block switches remain in place throughout the swimming meet and do not require any attention from the meet offcials. Each time a swimmer makes a turn, the fact that he has touched the lane switch is recorded by the electronic circuits which in turn count the laps and automatically stop the time read-outs on the final touch after the preset number of laps have been completed. The circuit is designed so'that a swimmer can touch the lane switches several times in making a turn and only the first touch will result in activating the lap counter.

6. The starting block switches are similar indesign to the lane switches and are activated by the swimmer standing on the switch and then leaving the switch. Since these switches are also sensitive on the top,

front, and front edge, if any part of the swimmers With the foregoing more important objects and features in view and such other objects and features which may become apparent as this specification proceeds, the invention will be understood from the following description taken in conjunction with the accompanying drawings, wherein like characters of references designate like parts, and wherein: I v

FIG. 1 is a perspective view illustrating the use of the invention in a swimming pool as a sensor for detecting events in a swimming meet; I

FIG. 2 is a vertical cross sectional view taken on line 2-2 in FIG. 1; I

FIG. 3 is an electrical diagrammatic view of the starting block switch illustrated in FIG. 2;'

FIG. 4 is a vertical cross sectional view taken 'on line 44 in FIG. 1;

FIG. 5 is an electrical diagrammatic view of the swimming lane switch illustrated in FIG. 4; Y

FIG. 6 is a perspective view of the" starting block switch of this invention with portions b'rokenaway to reveal underlying portions;

FIG. 7 is a perspective view of the lane switch of this invention in a partially assembled condition,

FIG. 8 is a perspective view of the lane switch of this invention in a further stage of assembly;

FIG. 9 is a perspective view of the upper portion of the lane switch of this invention in'an advanced stage of assembly with a portion broken away to show underlying parts; v

FIG. 10 is a perspective view of the top portion of the lane switch of this invention with its flexible cover removed;

FIG. 11 is a perspective view of the'assernbled lane switch of this invention with its mounting bracket separated therefrom;

FIG. 12 is a perspective view of a detail of the lane switch of this invention;

FIG. 12a is a perspective view of one of the anchor nuts used in the invention as shown in FIG. 12;

FIG. 13 is an electrical schematic diagram of the interface circuit used in this invention;

FIG. 14 is an exploded view ofa portion of the apparatus shown in FIG. 4. I

Referring now to the drawings the switches and l 1 of this invention are illustrated in FIG. l in use in the environment of a swimming pool 12 during a swimming meet in which swimmers l4 are shown. poised on the starting block switches 1] ready to dive into the water 13 when the starting signal is given. The starting block switches 11 are especially constructed switches which are mounted on top of the starting blocks.17 and extend over the front edge of the starting block. The switches 11 have a top portion 15 which is sensitive to the weight of the swimmer standing thereon and a front edge portion 16 which is sensitive to the pressure of a swimmers toes as the swimmer propells himself forward in a dive off the starting block 17. The starting blocks 17 are aligned adjacent the edge of the swimming pool apron 18 at one end of the swimming pool andare spaced so that each block is approximately at the center of one of a plurality of swimming lanes usually marked by lines (not shown) along the end walls and bottom of the swimming pool. The lane switches 10 are hooked over the top edge 19 of the gutter 20 by cured to the pool end wall by lag bolts (not shown) extending through mounting holes 68.

Looking now at the cross sectional view of the starting block switch 11 illustrated in FIG. 2, the switch comprises an angled backing plate 22, a top plate 23 spaced from the top portion 22a of backing plate 22 by spacers 24 and 25, a front plate 26 spaced from the front portion 22b of the backing plate by. spacers 27 and 28, and a flexible material outer protective covering 29 having a non-skid upper surface 29. The backing plate 22 is preferrably made from stainless steel to prevent corrosion and to provide one electrical contact of the starting block switch. Damping holes 30 are provided which extendthrough the backing plate 22'and permit the escape of fluid trapped between the flexible cover 29 and the plates23 and 26 as they are;moved toward the backing plate 22 by the weight of a swimmer standing on the starting block switch 1 l. The spacers 24, 25 are nonconductivetapes preferrably coated on opposite sides with waterproof adhesive to adhere to the outer face of the back plate 22 and to the inner face of top plate 23. Similarly the spacers 27 and 28 are non-conductive tapes'coated on opposite sides with waterproof adhesive to adhere to theouter face of front portion 22b of the backing plate-andto the inner face of the front plate 26. The spacers 24,25, 27 and 28 serve as insulators for spacing the top and front plates from the backing plate and for holding the top and front plates 23 and 26 respectively relative to the backing plate 22. The top plate 23 projects past the front portion 22b of the backing plate 22 and terminates in a downwardlyjcurved edge portion 31 which is spaced from and overlaps an upwardly projecting inwardly curved edge portion 32 of the front plate 26. The spacers 24 and 25 for the. top, plate 23 are substantially thicker than the spacers 27 and 28 for the front plate 26 in order that the curved edge portions 31 and32 will be spaced relative to each other in a substantially parallel relationship. The spacers supporting the top plate 23 and the front plate 26 are substantially removed from the free curved edge portions 31 and 32 in order that the curved edge portions function as cantilever beams. Weight applied downwardly on the top plate forward on the spacer 25 toward the curved edge 31 bends the curved edge 31 downwardly about the spacer 25 as a fulcrum. The curved edge 31 will slide over the curved edge portion 32 and force the curved edge 32 into contact with the backing plate 22 approximately the outer surface of the ninety degree comer portion 220 between the top portion 22a and the front portion 22b of the backing plate. The top plate 23 and the front plate 26 are preferably made of thin resilient stainless steel to prevent corrosion, and any hardware used in securing the starting block switchin position on the starting block 17 is also preferably of stainless steel. A conductive tape 33 is soldered or otherwise secured to the stainless steel front plate 26 and is joined inside the potted connector block 34 with one conductor 37 of a two conductor cable 36. The conductor 37 is the signal conductor and is connected to a suitable interface circuit such as the interface circuit illustrated in FIG. 13 which will be subsequently described. The second conductor 38 of the cable 36 is a ground or reference con ductor which is suitably connected to the backing plate 22 by soldering or other suitable electrical connecting means. The cable 36 is clamped to the backing plate 22 by a suitableclamp 35, and includes an end connector 36a for joining with a selected circuit.

The flexible cover 29 includes a rear section 290 and a front section 29b. The front section 29b is secured across the bottom edge of front plate 26 by non conductive, double faced, waterproof adhesive tape 33' and it extends upwardly over plate 26 and rearwardly over the front end portion 31 of the top plate 23 and is secured to the top plate 23 by a non conductive double faced, adhesive tape 110. The rear section 29a extends across the top of the top plate 23 from adjacent the rear edge of the front section 29b to the rear edge of the backing plate 22 where it is adhesively secured. The side edges of the flexible cover sections 29a and 29b are firmly held to the adhesive face of side marginal tape 111 extending outwardly beyond the side edges of plates 23 and 26and to a similar side marginal tape (not shown) on the opposite side of the plates 23 and 26.

FIG. 3, which is an electrical schematic diagram of the starting block switch 11, may be referred to for an understanding of the functionof the switch. Downward pressure on the top plate 23 near the cantilever end portion 31- as indicated by arrow 39 in FIG. 3 bends the end portion 31 downwardly into sliding engagement with the front plate 26 adjacent the cantilever end 32 thus forcing the cantilever end 32 downwardly into engagement with the backing plate 22 and completing a circuit between the signal conductor 37 and the ground conductor 38. As indicated in FIG. 1 the toes of a swimmer poised on the starting block for take off will normally be curved over the edge 31 of the top plate and maintain pressure thereon to close the switch. When the swimmer leaves the starting block, the edge portions 31 and 32 will return to the position shown in FIG. 2 because of the resiliency of the plates 23 and 26,

thus breaking the switch contacts.

Reference will now be made to the cross sectional view'of .the laneswitch illustrated in FIG. 4, and to the perspective views of the lane switch in various stages of assembly illustrated in FIGS. 7-11 in describing the lane switch. The lane switch 10 comprises an angled backing plate 50 having a horizontal top portion 50a and a frontportion 50b extending downwardly at a right angle to the top portion 50a, a top plate 51 spaced from the top portion 50a by a spacer tape 52, an intermediate plate 53 spaced from the front portion 50b of the backing plate by parallel, horizontal spacer strips 54, the inner leg 55a of u-folded tape 55, and vertical edge spacer strips 56 and 57, an outer plate 58 spaced from the intermediate plate 53 by parallel horizontal spacers 59 and the upfolded front portion 55b of the u-folded bottom spacer 55, a top leaf plate 64 spaced from the top plate 51 by spacer tape 65, and flexible protective cover tapes 66 and 67 secured around the peripheral edges of the outer plate 58.

FIG. 7 shows an early stage of the assembly of the lane switch with the intermediate plate 53 partially broken away to show the spacer strips 54 secured in place to the backing plate 50. The backing plate 50 is preferably made of stainless steel and serves as the grounded or reference electrode for the lane switch 10. Mounting holes 68 are provided along side edges of the backing plate through which anchor bolts or other suitable fas teners may be placed for securing the lane switch in more or less permanent position at one end of a swimming pool. The holes 69 along the front edge of the top portion 500 and extending through the front portion of the backing plate at intervals allow pool fluid to enter and leave the interior of the switch. The number and size of the holes 69 are selected to provide a damping action by only allowing the fluid to flow out from the interior of the switch at a preset rate, thereby, keeping waves and splashes from activating the switch 10. Damping holes can also be located in the material that covers the front edge. The spacer strips 54, 55a, 56, and 57 are non-conductive tapes coated on opposite sides with waterproof adhesive to adhere to the outer face of the backing plate 50 and to the inner face of the intermediate plate 53 which is held in position by the adhesive coated spacer tapes. The upper edge portion 53a of the intermediate plate is rolled to provide a rounded corner extending over the top front corner edge of the backing plate 50 and spaced from the backing plate by a gap equal to the thickness of the tape 54. The edge spacer strips 56 and 57 extend up the face of the front portion of the backing plate 50 and across the top portion 50a thereof. A plastic terminal block 70 is provided at one corner of the upper portion 500 for joining a dual conductor cable 74 with connectors from the switch contacts. The terminal block 70 is an open top plastic receptacle for receiving a potting compound to encase the switch terminals. An aperture 72 is provided in one end of the terminal block receptacle for receiving the cable ,74, and an aperture 73 is provided in the backing plate for securing a cable clamp 75 (see FIG. 11). A terminal strip 71 extends from the terminal block receptacle 70 to the inten'nediate plate 53 with which it is joined by solder or other suitable means to sages through the intermediate plate 53 in communication with the spaces on opposite sides thereof.

FIG. 8 shows the next stage of assembly of the switch 10 after that illustrated by FIG. 7. Non-conductive spacer strips 55b, 59, and 61 having opposite sides coated with a waterproof adhesive are shown applied to the outer face of the intermediate plate 53. The spacer strips 60 and 61 are superimposed over the spacer strips 56 and 57 respectively with the side edges of the intermediate plate 53 sandwiched inbetween. The outer leg 55b of the bottom spacer tape 55 is folded up and secured over the outer surface of the intermediate plate 53 adjacent its bottom edge (see FIG. 4). A thick spacer strip 52 having a thickness equal to the thickness of edge tapes 56 and 60 combined is positioned across the top portion 500 adjacent its rear edge so that the upper surface of strip 52 is flush with the upper surface of the portions of strips 60 and 61 extending across the top portion 50a of the backing plate. A filler strip 77 is provided between the terminal receptacle and the rear edge of the curved edge portion 53a of the intermediate plate which also is coated on both sides with waterproof adhesive and is of sufficient thickness so that its upper surface lies in the same plane with the upper surface of spacer strip 52. Each of the strips 59 is divided in two parts and separated by a gap 63 to provide a passage for fluid between spaces on opposite sides of the strips. The gaps 63 for the strips 59 are positioned along a diagonal line extending across the face of the intermediate plate 53 in a direction o'pposite to the diagonal line on which the gaps 62 (see FIG. 7) in the strips 54 are located. The switch assembly as shown in FIG. 8 is ready for the mounting of the top plate 51 over the spacer strips 52, 77 and portions of strips 60 and 61 extending over the upper portion of the backing plate 50. The front of the switch assembly as shown in FIG. 8 lacks only the mounting of anchors 78 across the top spacer strip 59 before the outer plate 58 can be superimposed thereon.

FIG. 9 shows the lane switch in another stage of assembly subsequent to the stage shown in FIG. 8. The top plate 51 having a front downwardly curved edge 51a is now mounted over the top portion 50a of the backing plate 50 and is held in place by the adhesive coated spacer strips 52, 60, 61 and 77. Anchors 78 having outwardly projecting hollow studs 80, (see FIG. 12 for an enlarged detail view) are shown mounted in a row across the top spacer strip 59 and projecting through apertures 81 along the top edge of plate 58. Referring to FIG. 12 one of the anchors 78 is shown adhered to the top row of waterproof adhesive tape 59 with the hollow stud projecting through aperture 81. Screw 79 and washer 79a (FIG. 14) clamp the protective flexible cover tape 67 to the plate 58 when installed in the hollow stud .80 of anchor 78. Adhesive coated spacer strip 59a is used to affix the flexible protective cover tape 67 to plate 58 between anchors 78.

The top plate 51 has a row of apertures 82 across its rear edge portion for receiving insulated screws (not shown). Corresponding apertures are provided through the spacer 52 and the top portion 50a of the backing plate 50 for receiving the insulated fastening screws. A pair of notches 83 are provided in the rear edge of the top plate 51 to expose the slots 85 in the backing plate 50a through which bolts may be extended to secure the mounting plate 21 to the backing plate. Terminal strip 86 is soldered or otherwise connected to make electrical contact with the top-plate 51and is superimposed over the terminal strip 71 within the terminal block receptacle 70 (see FIG. 10). The conductiveterminal strips 71 and 86-areadapted to be connected together and to the signal carrying conductor of cable 74 within the receptacle 70, and encased with potting material.

FIG. 10 shows still a subsequent stage of the switch assembly with a stainless steel top leaf plate 64 mounted over the top plate 51. Additional nonconductive spacer tapes 65, 88, 89, and 90 are provided to space the top leaf plate 64 above the top plate 51 (see FIG. 4). One end of the top leaf plate 64 is offset downwardly to provide a mounting tab 91 by which the top leaf plate 64 is connected in electrically conductive contact with the backing plate 50 by means of metal screws 92 extending through the tab 91 into the backing plate.

FIG. 11 shows the lane switch 10 completely assembled with the exception that the mounting plate 21 has been removed to show elongated slots 93 for adjustably receiving bolts 94 positioned in slots 85 of the backing plate 50 for securing the backing plate and mounting plate together. The borders of the front plate 58 are covered by black non-conductive border tapes 66, 67, 95 and 96 to outline the sensitive area of the switch in accordance with AAU rules. The border tapes also serve to cover the metal edges of the intermediate and outer plates 53 and 58. Tapes 66, 95, and 96 are coated on their'underside with waterproof adhesive so as to adhere both to the border edges of the outer plate 58 and to areas of the backing plate 50 bordering the outer plate 58. Notches 97 are provided in the edges of vertical border tapes 95 and 96 to expose'the mounting bolt holes 68. The flexible cover 67 has its front edge secured by means of the hollow rivets 80 which extend through apertures provided in the front edge of cover 67. The rear border of the cover 67 is secured over the top leaf plate 64 by insulated fasteners 98 extending through the cover 67, the spacer 87, top leaf plate 64, spacer 65, top'plate 51, and spacer 52 into the rear edge portion of back plate 50. A black cross 99 is painted on the front of the switch 10 in compliance with AAU rules. Normally the black cross is painted on the wall tiles of the swimming pool at the end of the lane; however, the walls are covered by the lane switch 10.

FIG. is an electrical schematic diagram of the lane switch 10. The top plate 51 and the center plate 53 are shown connected to the signal conductor 101 of the cable 74; they are separate elements connected 'together by terminal strips 71 and 86. The backing plate 50 is connected to the ground or reference conductor 102 of the cable 74 and is electrically connected to the outer plate 58 by conductive metal tape 103 soldered or otherwise electrically connected to the left hand border of the outer plate 58 and secured to the backing plate by means of a metal screw 104 (see FIG. 9). The top leaf plate 64 is electrically connected to the backing plate 50 by offset tab 91 and metal screws 92.

FIG. 13 shows a preferred electrical interface circuit which is used in conjunction with the lane and starting block switches and 11 separately for sensing the rectly to, the signal input terminal 105 and its base is connected to a voltage divider circuit including resistor R-l, diode D1 and resistor R2 connected in series circuit between voltage source V and the ground or reference conductor 106. The output from the collector of T1 is applied through a diode D2 to the base of transistor T2. The base of T2 is connected to the reference conductor 106 through base resistor R4. The emitter of transistor T2 is connected directly to the reference conductor 106 and the collector of T2 is connected to an output signal terminal 107. The interface circuit provides a voltage across the switch with which it is associated, for example the lane switch 10, low engough to prevent the ionization of the liquid medium (usually water) into which the switch may be immersed either partially or fully. Since the liquid is not ionized, the input transistor T1 is not conducting and the voltage at its collector terminal is high. This voltage turns on D2 and T2. The voltage at the collector of T2 is, therefore, low.

When the lane switch 10 is closed, Tl conducts and the voltage at the collector of T1 is low enough to cause D2 to open. T2 will, therefore, be nonconducting and the collector voltage at T2 is high.

The main novel feature of the interface circuit is that when it is used in conjunction with the switches 10 or 11 it will maintain the switch open circuit voltage below the ionization potential of the medium with which the switches are used. The switches are not sealed; therefore, the medium is continually between the switch layers. The potential across the switch plates can be adjusted by selecting the appropriate values of R1 and R2. D1 provides a voltage drop equal to the base to emitter voltage drop in T1. This insures that when the switch contact resistance (switch closure) is below approximately 15 ohms, T1 will conduct. Since the normal resistance of the liquid between the switch layers, in the case of the lane switch 10, exceeds 100 ohms with a small voltage potential between the switch plates, the closure of the switch causes the resistance to change from greater than ohms to less than 15 ohms. This fact is sensed by the electronic circuitand provides a'voltage change on the output terminal 107 to be utilized by suitable counters, timing circuits, judging circuits, and other indicators (not shown).

Other circuits can be used in conjuction with the lane and starting block switches, however, the voltage, current, resistance, or other type sensing circuit must operate with a voltage potential across the switch plates of a less value than the ionization potential of the medium between the plates.

Looking again at FIG. 4 it will be observed that the rows of horizontal double faced tapes 59 across the outer face of the intermediate plate 53 are staggered relative to the rows ofdouble faced tape 54 across the inner face of the intermediate plate 53. Such staggering opening or closure of the switches. Input terminals 105 and 106 of the interface circuit are adapted to be connected to the signal and ground conductors 101 and 102 of the lane switch 10, or to the signal and ground conductors 37 and 38 of the starting block switch ll by increases the sensitivity of the switch 10 to point contact'pressure; so that pressure applied to any point on the'front plate 58 within the sensitive area delineated byblack border=tape will cause the front plate 58 to touch the intermediate plate 53 and/or'the intermediate plate to touch the back plate. The thickness of the spacer tapes separating the different switch plates and the spacing between tapes in the same layer are important and are selected for optimum switch sensitivity. If the tapes-are too thick or theispacing between tapes is too little the switch will not be sensitive enough for young swimmers. Qn the other hand, if the thickness is too little and the spacing between tapes is too great, the switch will be too sensitive and may be acutated by waves in the pool 12. All of the spacer tapes are nonconductive and flexible.

In swimming competitions it has been found that inexperienced competitors would touch over the front top edge of the lane switch 10 on the back stroke, therefore, the top leaf plate 64 is added to increase the sensitivity of the top of the lane switch behind the front edge portion 51a. Since the lane switch 10 is flat on top and is on top of the gutter lip 19, contestants often stand on top of the lane switch in getting out of the pool 12. In order to prevent the top leaf plate from being permanently deformed by the weight of a person standing on top of the switch, the notches 100 (see FIG. 10) are provided on each side of the top leaf spring adjacent the spacers 89 and 90 and extending rearward from its front edge 108 so that the front edge portion of the top leaf plate 64 between the notches acts as a pure cantilever. Without the stress relieving notches 100, the weight of a person standing on top of the switch 10 would cause the stainless steel top leaf plate to be permanently bent at each edge and the switch would be shorted. The top leaf plate 64 is at the same potential as the back plate 50 when connected to the interface circuit shown in FIG. 13 and contact between the top leaf plate 64 and the top plate 51 will cause switch closure. Also contact between the top plate 51 and the back plate 50 will cause switch closure. The placement of the intermediate conductive plate 53 is critical because the top edge portion 530 is rolled or form-fitted to the comer portion 500 of the backing plate 50 leaving a gap equal to the thickness of tape 54. An important feature of this design is that the rolled over edge portion 530 cannot be permanently deformed by a person standing on the switch, hitting it with the hand or hitting it in any manner with a persons foot. The cantilever action of the intermediate plate 53 adjacent the edge portion 53a provides the sensitive touch contact across the front top curved edge 53a which enables the edge 53 after making contact with the back plate 50 to spring back into the position shown in FIG. 4 after the deforming force is removed. The top plate 51 is rolled or form fitted at its front edge 51a to overlap the upper edge portion 53a of the intermediate plate. Together the edge portions 51a and 53a will move in response to a small point pressure to make contact with the back plate 50. The sliding spring type action between the plates 51 and 53 will force the plates back into normal position when the pressure is removed.

The formation and placement of plates 23 and 26 of the starting block switch 11 with edge portions 31 and 32 rolled and overlapping in spaced relationship is comparable with the formation and placement of the plates 51 and 53 of the lane switch 10 and serves the same purpose. One of the outstanding features of the lane and starting block switches 10 and 1 1 is the sensitivity of their top front edges. This feature allows the lane switch 10 to be mounted on the gutter 20 at the end of the pool and to be held in place by a simple adjustable bracket 21. The lane switch 10 stays in place throughout a swimming contest and must, therefore, be sensitive on the front, top, and top front edge since it does not cover up the pool gutter. The sensitivity of the top front edge is accomplished by the sliding metal contacts of edge portions 51a and 53a in the lane switch 10 and the edge portions 31 and 32 in the starting block switch. Pressure directed toward the top, top front and front will cause the cantilevered curved metal plates to bend and contact each other in sliding contact and force the innermost plate into contact with the backing plate.

What is claimed is:

1. A switch for sensing swimming race events comprising in combination an angled conductive backing plate for mounting over the corner edge formed between the end wall of a swimming pool and a gutter lip having a top horizontal portion for overlying said gutter lip and a front portion joined to said top portion by a corner portion and extending downwardly therefrom, first nonconductive spacer means secured to said front portion, an intermediate conductive plate supported in spaced parallel relationship to said front portion of said backing plate by said first spacer means and provided with an upper curvededge portion overlying the corner portion of said backing plate in the manner of a cantilever beam, second non-conductive spacer. means se cured to said top portion, a top conductive resilient plate supported by said secondspacer means in spaced parallel relationship with said top portion and having a front downwardly curved edge portion overlying said upper curved edge portion in spaced substantially parallel relationship therewith, said top conductive plate being supported by said second spacer means in the manner of a cantilever beam, third non-conductive spacer means secured to the outer face of said intermediate plate, an outer resilient conductive plate, supported by said third spacer means in spaced parallel relationship with said intermediate conductive plate, and means electrically connecting said outer plate to said backing plate at the same potential, said first spacer means including multiple spaced rows of spacer strips between said intermediate plate and said backing plate with the topmost row being positioned a substantial distance below said upper curved edge portion, and said third spacer means including multiple spaced rows of spacer strips between said outer plate and said intermediate plate in spaced parallel relationship with the rows of said first spacer means and staggered with respect to the rows of said first spacer means, eachrow of spacer strips in said first and third spacer means including at least one pair of horizontally aligned spacers separated by a gap, the gap in the rows of said first spacer means being positioned along a first diagonal line extending across said intermediate plate and the gaps in the spacer rows of said third spacer means being positioned along a second diagonal line transverse to said first diagonal line.

2. The switch set forth in claim 1 wherein the backing plate has apertures extending therethrough to permit passage of a fluid medium at a selected rate of flow.

3. The combination comprising the switch set forth in claim 1 and an interface circuit means connected across said switch, said switch being open to the environment in which the switch is located to pennit a fluid medium from the environment to enter said switch and become interposed between said backing plate, said inresponsive to the closing of said switch to change said path from a'high impedance path to a low impedance path andresponsive to the opening of said switch to automatically change said path from a lowimpedance path to a high'impedance path. 4

4. The combination set forth in claim 3 for use in a swimming pool having an end'wall, a gutter lip, and a corner edge formed between the end wall and the gutter lip, water within said swimming pool and providing the fluid medium in which said switch is located when said top portion of said backing plate is mounted over said corner edge of said swimming pool.

5. The switch set forth in claim 1 together with fourth nonconductive spacer means secured to the upperface of said topplate and a conductive resilient top leaf plate supported by said fourth spacer means in parallel relationship with said top plate, said top leaf plate having a front edge portion which is supported in the man.-

ner of a cantilever beam, and means electrically connecting said top leaf plate to said backing plate at the same potential. w

6. The switch set forth in claim 5 wherein a pair of stress relieving notches are provided in the front edge portion-of said top leaf plate near the opposite side edges thereofyand wherein said fourth spacer means includes "spacer strips extending along the back edge and opposite side edges of said top plate outside of said stress relieving notches from the: center of said plate.

7. The switch according to claim 6 together with a flexible protective cover having a rear edge secured along the back edgeof said top. leaf plate and an opposite edge secured to said outer plate.

8. The switch set forth in claim 1- wherein said first spacer means also includes imperforate and uninterrupted spacer strips extending along the bottom and side'edges of the inner face of said intermediate plate, and said third spacer'means also includes imperforate and uninterrupted spacer strips extending along the bottom edge and side edgesof the outer face of said intermediate plate.

9. The swi-tch'according to claim 8together with bor- 1 der tapes adhesively secured to the bottom and opposite side borders of said outerplate and to adjacent areas of said backingplate bordering said outer plate,

said border tapes being waterproof and providing a seal between said outer plate and said backing plate.

10. The combination comprising an event sensing switch for use in a normally ionizable liquid medium having at least a pair of contacts which are normally switch, said interface circuit means including a signalinput conductor, a grounded reference conductor, an output conductor, said voltage source having one side connected to said reference conductor, a first transistor switch connectedbetween said signal input conductor and the ungrounded sideof said voltage source, a first bias means for biasing said first transistor switch to a high resistance state when said event sensing switch is open, a second transistor switchconnected between said reference conductor and the ungrounded side of said voltage source, a second bias means for said second transistor switch connected to said first transistor switch for sensing the resistance state of said first transistor switch and causing said second transistor switch to conduct when said first'transistor switch is in said high resistance state and causing said second transistor switch to open when said first transistor switch is in a low resistance state, said first transistor switch being biased to a low resistance when said event sensing switch is closed.

11. The combination comprising an event sensing switch for use in a normally ionizable liquid medium having at least a pair of contacts which are normally of said interface circuit'means for opening said bias controlled switch when said event sensing switch is open and for closing said bias controlled switch when said event sensing switch is closed, and means responsive tothe actuation of said bias controlled switch to its closed condition to produce an output signal indicating the closed condition of i said event sensing switch. 

1. A switch for sensing swimming race events comprising in combination an angled conductive backing plate for mounting over the corner edge formed between the end wall of a swimming pool and a gutter lip having a top horizontal portion for overlying said gutter lip and a front portion joined to said top portion by a corner portion and extending downwardly therefrom, first nonconductive spacer means secured to said front portion, an intermediate conductive plate supported in spaced parallel relationship to said front portion of said backing plate by said first spacer means and provided with an upper curved edge portion overlying the corner portion of said backing plate in the manner of a cantilever beam, second non-conductive spacer means secured to said top portion, a top conductive resilient plate supported by said second spacer means in spaced parallel relationship with said top portion and having a front downwardly curved edge portion overlying said upper curved edge portion in spaced substantially parallel relationship therewith, said top conductive plate being supported by said second spacer means in the manner of a cantilever beam, third non-conductive spacer means secured to the outer face of said intermediate plate, an outer resilient conductive plate supported by said third spacer means in spaced parallel relationship with said intermediate conductive plate, and means electrically connecting said outer plate to said backing plate at the same potential, said first spacer means including multiple spaced rows of spacer strips between said intermediate plate and said backing plate with the topmost row being positioned a substantial distance below said upper curved edge portion, and said third spacer means including multiple spaced rows of spacer strips between said outer plate and said intermediate plate in spaced parallel relationship with the rows of said first spacer means and staggered with respect to the rows of said first spacer means, each row of spacer strips in said first and third spacer means including at least one pair of horiZontally aligned spacers separated by a gap, the gap in the rows of said first spacer means being positioned along a first diagonal line extending across said intermediate plate and the gaps in the spacer rows of said third spacer means being positioned along a second diagonal line transverse to said first diagonal line.
 2. The switch set forth in claim 1 wherein the backing plate has apertures extending therethrough to permit passage of a fluid medium at a selected rate of flow.
 3. The combination comprising the switch set forth in claim 1 and an interface circuit means connected across said switch, said switch being open to the environment in which the switch is located to permit a fluid medium from the environment to enter said switch and become interposed between said backing plate, said intermediate plate and said outer conductive plate, said interface circuit means being connected electrically across said backing plate and said intermediate plate for normally providing a high impedance path between a voltage source and said switch when said switch is open to prevent the ionization of the fluid medium and the shorting of said switch by said fluid medium, and when said switch is closed for providing a low impedance path between said voltage source and said switch, said interface circuit means being automatically responsive to the closing of said switch to change said path from a high impedance path to a low impedance path and responsive to the opening of said switch to automatically change said path from a low impedance path to a high impedance path.
 4. The combination set forth in claim 3 for use in a swimming pool having an end wall, a gutter lip, and a corner edge formed between the end wall and the gutter lip, water within said swimming pool and providing the fluid medium in which said switch is located when said top portion of said backing plate is mounted over said corner edge of said swimming pool.
 5. The switch set forth in claim 1 together with fourth nonconductive spacer means secured to the upperface of said top plate and a conductive resilient top leaf plate supported by said fourth spacer means in parallel relationship with said top plate, said top leaf plate having a front edge portion which is supported in the manner of a cantilever beam, and means electrically connecting said top leaf plate to said backing plate at the same potential.
 6. The switch set forth in claim 5 wherein a pair of stress relieving notches are provided in the front edge portion of said top leaf plate near the opposite side edges thereof, and wherein said fourth spacer means includes spacer strips extending along the back edge and opposite side edges of said top plate outside of said stress relieving notches from the center of said plate.
 7. The switch according to claim 6 together with a flexible protective cover having a rear edge secured along the back edge of said top leaf plate and an opposite edge secured to said outer plate.
 8. The switch set forth in claim 1 wherein said first spacer means also includes imperforate and uninterrupted spacer strips extending along the bottom and side edges of the inner face of said intermediate plate, and said third spacer means also includes imperforate and uninterrupted spacer strips extending along the bottom edge and side edges of the outer face of said intermediate plate.
 9. The switch according to claim 8 together with border tapes adhesively secured to the bottom and opposite side borders of said outer plate and to adjacent areas of said backing plate bordering said outer plate, said border tapes being waterproof and providing a seal between said outer plate and said backing plate.
 10. The combination comprising an event sensing switch for use in a normally ionizable liquid medium having at least a pair of contacts which are normally spaced from each other in the open condition of said switch, at least one of said contacts being movable relative to the other contact to close said switch, and an interface circuit means connected to said pair of switch contacts and to a voltage source for providing a sufficiently low voltage across said pair of switch contacts when said contacts are open and immersed in said liquid medium to prevent ionization of said liquid medium and which, when said switch is closed, will provide an output signal indicating the closed condition of said switch, said interface circuit means including a signal input conductor, a grounded reference conductor, an output conductor, said voltage source having one side connected to said reference conductor, a first transistor switch connected between said signal input conductor and the ungrounded side of said voltage source, a first bias means for biasing said first transistor switch to a high resistance state when said event sensing switch is open, a second transistor switch connected between said reference conductor and the ungrounded side of said voltage source, a second bias means for said second transistor switch connected to said first transistor switch for sensing the resistance state of said first transistor switch and causing said second transistor switch to conduct when said first transistor switch is in said high resistance state and causing said second transistor switch to open when said first transistor switch is in a low resistance state, said first transistor switch being biased to a low resistance when said event sensing switch is closed.
 11. The combination comprising an event sensing switch for use in a normally ionizable liquid medium having at least a pair of contacts which are normally spaced from each other in the open condition of said switch, said switch having fluid passage means for permitting said liquid medium from a surrounding environment to enter between the switch contacts, a voltage source which is normally sufficient to ionize said liquid medium, and an interface circuit means connected between said voltage source and said pair of switch contacts, said interface circuit means including a bias controlled switch connected in series circuit with said voltage source and said event sensing switch, a bias circuit means responsive to the open and closed condition of said interface circuit means for opening said bias controlled switch when said event sensing switch is open and for closing said bias controlled switch when said event sensing switch is closed, and means responsive to the actuation of said bias controlled switch to its closed condition to produce an output signal indicating the closed condition of said event sensing switch. 